Answer
c and d. Stages 3 and 4 of NREM sleep. These are the stages of deep sleep dominated by EEG delta waves.
Work Step by Step
Stages 2 and 3 of NREM sleep are stages of deep sleep in which arousal is difficult . Vital signs begin to decline in Stage 3. Nightmares , night terrors and sleep walking are more likely to occur in Stage 4.. Some psychologists diffrentiate between night terrors and night mares. Nightmares are often defined simply as bad dreams.
